The invention generally relates to ink jet printer apparatus and methods and more particularly relates to ink jet printers which are capable of providing variable ink drop volumes at different pixel locations.
An ink jet printer produces images on a receiver by ejecting ink drops onto the receiver in image wise fashion. The advantages of nonimpact, low-noise, low energy use, and low-cost operation in addition to the capability of the printer to print on plain paper and upon various coated papers are largely responsible for the wide acceptance of ink jet printers in the marketplace.
In this regard, xe2x80x9ccontinuousxe2x80x9d ink jet printers utilize selective deposition of drops through control of deflection of the drops from the printer nozzle. A gutter may be used to intercept drops that are not intended to reach the receiver sheet in accordance with a determination based on image data of whether a drop of ink is to be deflected or not deflected.
Another class of ink jet printers are referred to as the drop-on-demand ink jet printers which provide at every nozzle orifice a pressurization actuator that is used to produce the inkjet drops. The actuators used in drop-on-demand inkjet printers normally include heat actuators or piezoelectric actuators. With regard to heat actuators, a heater placed at a convenient location within the nozzle or at the nozzle opening heats the ink in selected nozzles and causes a drop to be ejected to the recording medium in those nozzles selected in accordance with image data. With respect to piezoelectric actuators, a piezoelectric material is used, which piezoelectric material possesses the property such that when an electrical field is applied to the material a mechanical stress is induced therein reducing the volume of a nozzle and causing a drop to be selectively ejected from the nozzle selected. Image data applied to the print head determines which of the nozzles are selected for ejection of a respective droplet from each nozzle at a particular pixel location on a receiver sheet. Some drop-on-demand inkjet printers described in the patent literature use both piezoelectric actuators and heat actuators.
As ink jet printers have advanced to the point where it is now possible to place different drop volumes of ink at different pixel locations, it is desirable that methods to optimize drop volumes and drop volume placement be used to optimize the image quality of hard copy images.
Given that ink jet printers are capable of rendering images using different drop volumes of ink at different pixel locations, is noted, however, that this capability is somewhat limited. It is desirable therefore to provide an inkjet printer and method of printing wherein the effective number of gray levels printable by an ink jet printer may be increased.
The above and other objects which will become apparent after reading the specification herein are accomplished in accordance with the subject matter described in the independent claims appended hereto.